Dairy cattle crossbreeding in the tropics: Choice of crossbreeding strategy

Summary Two strategies for crossbreeding of indigenous and exotic cattle for milk production in the tropics,viz. rotational crossing and formation of a composite breed, have been compared. Genetic considerations suggest that rotational crossing would lead to somewhat better dairy performance, mainly because of more heterozygosity. Predictions based on the performance of adjacent genetic groups as obtained from a comprehensive literature review point in the same direction.Rotational crossbreeding depends on a continuous introduction of bulls of both parental breeds. The herd will consist of 2 (or more) genetic groups, which might be inconvenient for breeding arrangements, but provides more flexibility. The system requires good organisation and is most suitable in large farms. In small scale dairying the composite breed strategy is the most practical approach to dairy cattle breeding in the tropics.

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Cruzamiento De Vacuno Lechero En Los Tropicos: Eleccion De La Estrategia De Cruzamiento

Resumen El artículo compara dos estrategias de cruzamiento entre vacuno lechero exótico e indígena en los trópicos: el cruzamiento rotativo y la formación de una raza híbrida. Las consideraciones genéticas sugieren que el cruzamiento rotativo debería llevar a una mejor producción lechera, sobre todo debido a un aumento de la heterozigosis. Las predicciones basadas en el rendimiento de grupos genéticos adyacentes determinado a partir de una revisión bibliográfica apuntan en la misma dirección.El cruzamiento rotativo require una introducción contínua de toros de las dos razas parentales. El rebaño consistiría de 2 (o más) grupos genéticos, lo que -si bien permite una mayor flexibilidad- puede dificultar la planificación de la reproducción. El sistema requiere una buena organización y resulta más factible en explotaciones grandes. En explotaciones pequeñas de los trópicos, la formación de una raza híbrida es la estrategia más prática en lo que a cría de vacuno lechero se refiere.

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Croisement Du Cheptel Laitier Sous Les Tropiques: Choix De La Strategie De Croisement

Résumé Deux stratégies pour le croisement entre le bétail indigène et le bétail exotique pour la production laitière sous les Tropiques, à savoir le croisement rotationnel et la formation d'une race composite, ont été comparées. Des considérations génétiques suggèrent que le croisement rotationnel amènerait quelque chose de plus performant au niveau laitièr, principalement dù à l'augmentation de hétérozygotie. Des prédictions, basées sur les performances de groupes génétiques adjacents, issues de l'étude complète de la littérature donnent la même analyse.Le croisement rotationnel est basé sur l'introduction continuelle de taureaux venant des deux races parentales. La horde consistera en 2 (ou plus) groupes génétiques, ce qui peut être gênant pour le croisement mais permet plus de flexibilité. Le système demande une bonne organisation et est préférable dans les grandes fermes. A une échelle de production laitiere plus faible la stratégie de la race composite est l'approche la plus pratique pour le croisement du cheptel laitier sous les Tropiques.

     

Influence of season of birth on weight for age in two genetic groups of cattle

Summary Body weights from birth to 756 days of age for calves of Mpwapwa cattle (12%Bos taurus inheritance) and backcrosses (34%Bos taurus) born in the wet or the dry season were analysed. The calves were weaned at 75 days of age and after that fed entirely on pasture. Backcrosses were heavier than Mpwapwa at birth and at 252 days of age but not at subsequent ages. Calves born in the dry season had slightly larger birth weights than calves born in the wet season. Weight differences were reversed from 252 to 504 days reflecting the seasonal fluctuations in grass growth. The effect of season of birth on long term rate of gain was negligible. No significant interaction between genetic group (Mpwapwavs backcrosses) and season of birth (wetvs dry) was observed at any of the ages. The study thus did not confirm the hypothesis that backcrosses because of their higher proportion ofBos taurus genes were more sensitive to the nutritional stress of the dry season than were pure Mpwapwa calves.

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Resumem Se analizaron los pesos corporales desde el naciminento hasta los 756 días, de terneros Mpwapwa (12% de herencia deBos taurus) y retrocruces (34%Bos taurus) en la estación lluviosa y seca. Los terneros se destetaron a los 75 días de edad, manteniendose con pasto únicamente de ahí en adelante. Los retrocruces pesaron más al nacer y a los 252 días de edad, pero nó en adelante. Los terneros nacidos en la estación seca, pesaron un poco más que los nacidos en la lluviosa. Las diferencias de peso fueron contrárias, de los 252 a los 504 días, reflejando las fluctuaciones estacionales en el crecimiento de pasto. La influencia estacional al nacer, sobre la tasa de ganancia de peso a largo tiempo, no fue importante. No se observó una interacción significativa, entre grupos généticos (Mpwapwavs retrocruces) y la influencia de la estación al nacer (lluviosavs. seca) en ninguna de las edades. Este estudio, no confirmó la hipótesis que los retrocruces, debido a la más alta proporción de genesBos taurus, eran más sensitivos al estrés nutricional durante la estación seca, que los puros Mpwapwa.

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Résumé On a analysé les poids corporels de la naissance au 756 ème jour de veaux Mpwapwa (12% de sangBos taurus) et de croisements de retours (34%Bos taurus) nés en saison de pluies ou en saison sèche. Les veaux ont été sevrés à l’age de 75 jours puis nourris intégralement au paturage. Les croisés sont plus lourds que les Mpwapwa à la naissance et au 252 ème jour, mais non à un age plus avancé. Les veaux nés en saison séche ont des poids à la naissance lég rement plus élevés que ceux nés en saison des pluies. Les différences de poids sont inversées du 252 ème au 504 ème jour, reflètant les fluctuations saisonnières de la croissance de l’herbe. L’effet de la saison de naissance sur le gain de poids à long terme est négligeable. On n’a observé aucune interaction significative entre les groupes génétiques (Mpwapwavs croisés) ou la saison de naissance (pluies,vs saison sèche). L’étude ne confirme donc pas l’hypothèse que les croisés, par suite de leur proportion supérieure de gènesBos taurus sont plus sensibles au stress nutritionel de la saison sèche que le sont les veaux Mpwapwa purs.

     

西门塔尔牛、安格斯牛杂交生产利用研究

为了探讨西门塔尔牛和安格斯牛杂交改良本地黄牛效果,采用西门塔尔牛和安格斯牛作为肉牛终端父本,分别与本地黄牛开展二元经济杂交,对杂交F1体重变化、屠宰性能数据进行了统计分析研究。结果表明：两者杂交F1均比本地黄牛生长速度快且产肉率高,可有效提高本地黄牛的屠宰性能。说明西门塔尔牛和安格斯牛改良本地黄牛杂交优势明显,可有效增加本地黄牛养殖的经济效益,值得推广。     

Influence of calving season and stocking rate on birth weight and weaning weight of Simmental-sired calves from Brahman-Hereford F1 dams.

Braham-Hereford F1 dams have been used to evaluate the influence of grazing pressure on forage attributes and animal performance at the Texas A&M University Agricultural Research Center at Overton. Data for this study were compiled from 1,909 records of Simmental-sired calves born to Braham-Hereford F1 cows from 1975 to 1990. Birth weight and weaning weight were analyzed independently to estimate the influence of year, season of birth, dam age, weaning age, and sex of calf. The effect of stocking rate as represented by levels of forage availability on weaning weights and subsequent birth weights was measured. Within the fall and winter calving seasons, lactating dams grazing at a high stocking rate produced calves with the lowest subsequent birth weights. Lactating dams assigned to creep-fed treatments had calves with the heaviest subsequent birth weights. Although dams that were less than 3.5 yr of age had calves with the lightest birth weights, there was no apparent decline in birth weight of calves from dams 12 to 17 yr old. Year, sex of calf, age of dam, stocking rate, season of birth, age at weaning, and birth weight were significant factors affecting weaning weight (P less than .01). Fall-born calves grazing cool-season annual pastures were heavier at weaning (267.6 kg) than either winter- (252.0 kg) or spring-born calves (240.9 kg). A stocking rate x season-of-birth interaction was observed for birth weight and weaning weight (P less than .05). Differences in weaning weight from low- vs high-stocked pastures were greater for fall-born calves (61.6 kg) than for winter-born calves (48.7).(ABSTRACT TRUNCATED AT 250 WORDS)     

影响母猪产仔数和仔猪初生重的因素

繁殖率是反映母猪繁殖力和猪场生产管理水平的重要经济参数。通常衡量母猪群生产性能的指标是每头母猪每年提供的断奶仔猪数,主要有两部分组成,即年母猪产仔窝数和母猪每窝的断奶仔猪数。据生产实践,有许多因素影响着母猪的生产性能,包括遗传因素、环境因素、饲养管理因素等。饲养母猪,只有年产仔窝数多,     

Use of embryo transfer to induce twinning in beef cattle: embryo survival rate, gestation length, birth weight and weaning weight of calves

Experiments were conducted in 1985 and 1986 at the Eastern Ohio Resource Development Center, Belle Valley, to examine the feasibility of using embryo transfer to induce twinning and to examine the influence of twinning on traits of the cow and calf. Embryos were collected from a total of 14 superovulated Angus donors on two dates each in 1985 and 1986 and were transferred to Angus recipients. A total of 124 embryos were transferred to 79 recipients, with 43 (34.7%) calves born alive. Seven of 45 (15.6%) recipients implanted with two embryos produced twins. In no case did both halves of the 15 embryos that were split to produce identical twins and implanted in the same recipient survive to birth. Proportion of calves born alive did not differ among transfer codes 3 (nonsplit embryos from two different donors implanted in separate uterine horns of the same recipient), 6 (nonsplit embryos from one embryo flush implanted in separate uterine horns of the same recipient) and 7 (nonsplit embryos from two different donors implanted in the same uterine horn of one recipient). Surgical transfers tended to result in a higher proportion of embryos surviving to birth (.43 vs .21; P = .16) and a higher twinning rate (.29 vs .04; P = .36) than did nonsurgical transfers. Age of recipient did not influence embryo survival (P = .98) or twinning rate (P = .99). Gestation length was 5 d shorter (P less than .01) for twin calves than for singles. Singles were 9 kg heavier (P less than .01) at birth and 32 kg heavier (P less than .01) at weaning than twins. However, cows raising twins produced 108 kg (51%) more total weaning weight than did cows raising singles.     

Genetic parameters of postnatal mortality and birth weight in Japanese Black calves

Postnatal mortality (PM) of calves is an economically important trait, because a high mortality rate of calves decreases farm income and significantly increases production costs. In spite of the economic importance of PM, genetic studies on PM have been scarce for Japanese Black cattle. The objectives of this study were to estimate the direct and maternal heritability for PM using a Bayesian threshold model with Gibbs sampling in Japanese Black cattle. The original data consisted of 43 723 records of animals born from January 2005 to June 2006. Four binary traits of mortality were considered: D1‐14, D15‐60, D61‐180 and D1‐180 with numbers indicating the period of risk in days after birth. Direct heritabilities for PM ranged from 0.12 to 0.31 and maternal heritabilities for PM were lower than the direct heritabilities and ranged from 0.02 to 0.16. Direct genetic correlations between D1‐14 and D15‐60, between D15‐60 and D61‐180, and between D1‐14 and D61‐180 were 0.501, 0.689 and 0.062, respectively. Direct genetic correlations of birth weight with D1‐14, D15‐60, D61‐180 and D1‐180 were 0.089, 0.482, 0.434 and 0.394, respectively. These results indicated that different genes were responsible for early and late PM and early PM (D1‐14) can be genetically reduced without influencing birth weight.     

Influence of Bos indicus crossbreeding and cattle age on apparent utilization of a high-grain diet

Ten Bos indicus x MARC III (initial BW = 303 +/- 25 kg) and 10 MARC III (initial BW = 322 +/- 16 kg) steers were used in a 2 x 2 factorial design to determine whether cattle age or Bos indicus crossbreeding influence site of digestion of a high-grain diet. Initially, five Bos indicus x MARC III and five MARC III steers were fitted with duodenal cannulas and adapted to a 95% concentrate diet that was offered for ad libitum consumption for a 237-d feeding period (calves). During the feeding period, duodenal and fecal samples were collected during 4-d periods beginning on d 14, 67, 137, and 228. The remaining 10 steers were fed a forage-based diet for a targeted daily gain of .6 to .7 kg for 210 d (yearlings). Following this period, yearling steers were duodenally cannulated and adapted to the 95% concentrate diet. Yearling steers had ad libitum access to feed for 165 d, and samples were collected during 4-d periods beginning on d 13, 42, 102, and 159. Dry matter intake was 9.8 and 7.6 kg/d and daily gain was 1.35 and 1.16 kg in yearlings and calves, respectively. Apparent OM digestion in the stomach was greater (P < .01) in yearlings than in calves. In contrast, postruminal disappearance as a percentage of OM intake was greater (P = .05) in calves than in yearlings. Duodenal flows of total N, microbial N, nonmicrobial N, and total amino acids and total tract N digestibility were not affected (P > .05) by age or Bos indicus crossbreeding. Fecal N excretion was greater (P < .01) in yearlings than in calves. Results of this experiment suggest little effect of Bos indicus influence on utilization of a high-grain diet. However, more feed is digested in the rumen of yearlings than of calves consuming a high-grain diet.     

Effect of birth date on growth performance of calves of seasonally-bred range cattle

SUMMARY: This study was undertaken to investigate the relationship between date of birth and growth performance of calves born to seasonally-bred range beef cows. Late-born calves exhibited an apparent superiority in preweaning growth over that of their early-born counterparts. This was attributed to a positive residual effect of maternal environment arising from the fact that calves born late were those whose dams had a substantial proportion of the critical last trimester of the gestation period in a favourable season. This advantage soon disappeared and early-born calves gained more weight and at a faster rate between 90 days and weaning. A combination of the effect of weaning stress and unfavourable nutritional environment in the immediate postweaning period had a check on calf growth but late born calves suffered most. It was concluded that, in this environment, nutrition was most limiting to calf growth between weaning and 12 months of age and it was during this period that a clear advantage of early birth of calves appeared; A 1 day delay in BD was associated with a 9.1 kg (P < .01) decrease in net weight change in this period. However, due to compensatory growth, the corresponding figure for the 12 months to 18 months period was an increase of 11.6 kg (P < .01) in weight change. In terms of actual postweaning weights (not age-adjusted), early BD was superior to late BD at all ages except at 18 month. A 1 day delay in BD was associated with a .7 kg reduction (P < .01) in liveweight between 90 days and weaning, a 6.7 kg reduction (P < .01) in actual weaning weight, a 6.8 kg reduction (P < .01) in actual 12 months liveweight, and a non significant (P > .05) 0.7 kg reduction in actual 18 months liveweight. Under seasonal breeding and group management of calves, all animals from a calf crop are expected to go to market at the same time, thereby rendering age-adjustment of liveweights irrelevant. However, the sale of late calves could be delayed by a few months to take advantage of the rainy season and to exploit compensatory growth. The benefit of this practice should, however, be weighed against both the direct cost (of feeding, veterinary care, labour and so on) and the indirect cost - the competition factor -introduced on the next calf crop. ZUSAMMENFASSUNG: Beziehung zwischen Geburtsdatum und Wachstumsleistung von K?lbern saisongedeckter Fleischrinder Sp?tgeborene K?lber zeigten eine scheinbare überlegenheit im Saugperiodenwachstum, was den positiven Restwirkungen maternaler Umwelt zugeschrieben wird, die auf günstige Umwelteinflüsse w?hrend des letzten, dann regenreichen Trimesters der Tr?chtigkeitsperiode zurückzuführen sind. Dieser Vorteil ist bald verschwunden, und frühgeborene K?lber hatten ein rascheres Wachstum zwischen 90 Tagen und dem Absetzen. Eine Kombination von Absetzstre? und ungünstiger Ern?hrungssituation unmittelbar nach dem Absetzen bremste das Jungtierwachstum, wobei sp?tgeborene K?lber den meisten Schaden zeigten. In der gegebenen Umwelt hat mangelnde Ern?hrung den st?rksten begrenzenden Einflu? auf Wachstum zwischen Absetzen und J?hrlingsalter, so da? sich in dieser Periode der Vorteil von frühen Geburten zeigte. Eine Verz?gerung von 1 Tag bei der Geburtszeit führte zu 9,1 kg Verminderung des Nettogewichts-Zuwachses in dieser Periode. Aufgrund kompensatorischen Wachstums ?nderte sich das zwischen 12 und 18 Monaten auf plus 11,6 kg Zuwachs. In bezug auf Jungtiergewichte (nicht alterskorrigiert) waren Tiere mit frühem Geburtsdatum in allen Altersklassen, au?er bei 18 Monaten, überlegen. Eine Verz?gerung von 1 Tag im Geburtsdatum war verbunden mit 0,7 kg Reduktion im K?rpergewichtszuwachs zwischen 90 Tagen und Absetzen, mit einer 6,7 kg Reduktion im Absatzgewicht und 6,8 kg im J?hrlingsgewicht. Das 18 Monate Gewicht war insignifikant um 0,7 kg reduziert. Unter saisonaler Zucht und Management gehen alle Tiere zur selben Zeit auf den Markt, so da? Alterskorrekturen irrelevant sind. Allerdings k?nnte der Verkauf sp?tgeborener K?lber um einige Monate verz?gert werden, um die Vorteile der Regenzeit und des damit verbundenen kompensatorischen Wachstums auszunutzen. Vorteile einer solchen Praxis aber sollten sowohl gegen die direkten (Futter, Veterin?re, Arbeit usw). wie auch gegen indirekte Kosten (Wettbewerb durch die n?chsten K?lber) balanciert werden.     

Maternal birth weight breeding value as an additional factor to predict calf birth weight in beef cattle

A total of 1,028 birth weight (BWT) and gestation length (GL) records were collected for calves from 1994 to 1997 in five U.S. Angus herds. Parental BWT EPD and dam BWT maternal breeding values (MBV) computed from the entire U.S. Angus data base after each breeding season were also available. A full model was fit to BWT that contained contemporary group (CG), sire BWT EPD, dam BWT EPD, and dam BWT MBV. A reduced model that dropped dam BWT MBV was also fit. The full model had smaller (P < .01) sum of squares for error than the reduced model. Calf BWT records were then adjusted for CG. Two data sets were formed to include adjusted BWT progeny records from sires with BWT EPD > or = .75 or > or = 1.0 SD above the mean of sires in the data set. Adjusted birth weights were assigned to either > or = .75 or other < .75 SD and > or = 1.0 or < 1.0 SD categories based on the mean BWT of calves in the entire data set. Dams were assigned to either > or =2 .75 or < .75 SD and > or = 1.0 or < 1.0 SD categories based on dam BWT EPD, MBV, or total maternal genetic contribution (TMGC = EPD + MBV). Chi-square analyses showed that dam BWT EPD, MBV, or TMGC categories were not independent (P < .10) of BWT SD categories, indicating that both dam BWT EPD and BWT MBV provide useful information to attenuate calf BWT. Calf BWT records were then adjusted for the overall mean, CG, sire and dam BWT EPD, and dam BWT MBV. Dams were then assigned to five categories: high dam EPD and MBV (HH), high dam EPD and low MBV (HL), low dam EPD and high MBV (LH), low dam EPD and MBV (LL), and other (OTH). High was > or = .75 or > or = 1.0 SD and low was < .75 or < 1.0 SD based on the mean BWT EPD or MBV of dams in the data set. In all adjusted BWT analyses, HH, HL, and LH categories did not differ (P > .05) from each other; however, the LL category was less (P < .05) than all other categories, indicating that calves from LL dams were lighter at birth than expected. For GL, LL was significantly different (P < .05) from only HH. The large differences in birth weight for the LL dams compared to other groups did not seem to be primarily due to shorter GL. Results showed that MBV provided additional information to control BWT; however, when both dam MBV and EPD were low, birth weight of calves was less than expected. Future research should focus on explanations for this interaction.     

加系纯种肉牛改良本地黄牛效果的调查研究

选用西门塔尔、夏洛来、利木赞3个品种公牛48头,用来改良本地黄牛,培育优质肉午。对种公牛后裔的出生、6月龄、12月龄体重、体尺进行测定及屠宰试验。经统计分析,对引进种公牛的种用价值进行评定,比较了西门塔尔、夏洛来、利木赞3个品种及品种内个体的改良效果。     

仔猪初生重的影响因素及提高措施

仔猪初生重是衡量猪的一个重要种质性状,初生重影响猪一生的生长发育、生产性能和宰后胴体等级等。仔猪初生重与肉猪的出栏体重呈正相关,与出栏日龄呈负相关。据报道,初生重低于1．0kg的仔猪,大多生长发育不良,1．5kg以上则发育明显较好。因此,有针对性地提高仔猪初生重,对于养殖生产具有重要意义。